The present invention relates to an improvement in liquid-liquid exchangers, particularly extraction columns, of the type in which a dispersed phase circulates in a continuous phase in countercurrent or counterflow form.
It uses known procedures of electrostatic settlers for the separation of the emulsions, i.e. settlers provided with electrodes producing an electric field ensuring the coalescence of the drops of the emulsion. Such equipment is widely used in water in oil separation.
U.S. Pat. No. 4,161,439 proposes a multistage liquid-liquid exchanger comprising, in regularly distributed manner, dispersion and electrocoalescence zones, i.e. zones in which are produced electrical fields respectively, ensuring the dispersion and coalescence of the drops of the dispersed phase.
The exchanger described in this patent has a single column in which, in the active part, is located a plurality of electrocoalescers and effective separation of the two liquids leaving the column is not sought, so that it is possible to associate several exchange or rectifying columns in series.
It is known that the performance levels of liquid-liquid exchangers having a dispersed phase in a continuous phase increase with the size of the specific interfacial area of contact between the two phases. They must operate with a high retention level which, unfortunately, can lead to a significant entrainment of the dispersed phase in the continuous phase leaving the exchanger.